Engineers typically design high-pressure oil field plunger pumps in two sections; the (proximal) power section and the (distal) fluid section which are connected by multiple stayrods. The power section, illustrated in FIG. 1, usually comprises a crankshaft, reduction gears, bearings, connecting rods, crossheads, crosshead extension rods, etc. Commonly used fluid sections usually comprise a plunger pump housing having a suction valve in a suction bore, a discharge valve in a discharge bore, an access bore, and a plunger in a plunger bore, plus high-pressure seals, retainers, etc. FIG. 1 illustrates a typical fluid section showing its connection to a power section by stay rods. A plurality of fluid cylinders similar to that illustrated in FIG. 1 may be combined, as suggested in the Quini-plex or five cylinder fluid section housing illustrated in FIG. 1. Fluid sections also include a suction manifold to supply fluid to the suction bore and suction valve. The suction manifold is typically attached to the fluid section by bolts. The suction manifold is typically connected to external piping used to supply fluid to the manifold by a tubular connection on either end of the suction manifold. The discharge manifold which allows for the exit of the pumped high pressure fluid is usually integral to the fluid section.
Valve terminology varies according to the industry (e.g., pipeline or oil field service) in which the valve is used. In some applications, the term “valve” means just the valve body, which reversibly seals against the valve seat. In other applications, the term “valve” includes components in addition to the valve body, such as the valve seat and the housing that contains the valve body and valve seat. A valve as described herein comprises a valve body and a corresponding valve seat, the valve body typically incorporating an elastomeric seal within a peripheral seal retention groove.
Valves can be mounted in the fluid end of a high-pressure pump incorporating positive displacement pistons or plungers in multiple cylinders. Such valves typically experience high pressures and repetitive impact loading of the valve body and valve seat. These severe operating conditions have in the past often resulted in leakage and/or premature valve failure due to metal wear and fatigue. In overcoming such failure modes, special attention is focused on valve sealing surfaces (contact areas) where the valve body contacts the valve seat intermittently for reversibly blocking fluid flow through a valve.
Valve sealing surfaces are subject to exceptionally harsh conditions in exploring and drilling for oil and gas, as well as in their production. For example, producers often must resort to “enhanced recovery” methods to insure that an oil well is producing at a rate that is profitable. And one of the most common methods of enhancing recovery from an oil well is known as fracturing. During fracturing, cracks are created in the rock of an oil bearing formation by application of high hydraulic pressure. Immediately following fracturing, a slurry comprising sand and/or other particulate material is pumped into the cracks under high pressure so they will remain propped open after hydraulic pressure is released from the well. With the cracks thus held open, the flow of oil through the rock formation toward the well is usually increased.
The industry term for particulate material in the slurry used to prop open the cracks created by fracturing is the propend. And in cases of very high pressures within a rock formation, the propend may comprise extremely small aluminum oxide spheres instead of sand. Aluminum oxide spheres may be preferred because their spherical shape gives them higher compressive strength than angular sand grains. Such high compressive strength is needed to withstand pressures tending to close cracks that were opened by fracturing. Unfortunately, both sand and aluminum oxide slurries are very abrasive, typically causing rapid wear of many component parts in the positive displacement plunger pumps through which they flow. Accelerated wear is particularly noticeable in plunger seals and in the suction (i.e., intake) and discharge valves of these pumps.
Back pressure tends to close each individual valve sequentially when downstream pressure exceeds upstream pressure. For example, back pressure is present on the suction valve during the pump plunger's pressure stroke (i.e., when internal pump pressure becomes higher than the pressure of the intake slurry stream. During each pressure stroke, when the intake slurry stream is thus blocked by a closed suction valve, internal pump pressure rises and slurry is discharged from the pump through a discharge valve. For a discharge valve, back pressure tending to close the valve arises whenever downstream pressure in the slurry stream (which remains relatively high) becomes greater than internal pump pressure (which is briefly reduced each time the pump plunger is withdrawn as more slurry is sucked into the pump through the open suction valve).
The suction manifold plays a vital role in the smooth operation of the pump and valve performance and life. All fluid entering the pump passes through the suction manifold. If the suction manifold is poorly designed, incomplete filling of the cylinder may result, which in turn leads to valves closing well after the end of the suction stroke, which in turn results in higher valve impact loads. High valve impact loads in turn result in high stress in the fluid end housing and ultimate premature failure of the valves, seats, and/or housing.
To insure complete filling of the cylinder requires fluid energy in the suction manifold and fluid energy in the cylinder during the suction stroke. The pumped fluid typically acquires fluid energy from the fluid pressure from a small supercharging pump immediately upstream from the pump of this invention. The fluid energy can be dissipated by turbulence or friction within the suction filling plumbing or line and in the suction manifold. Thus the design of the suction manifold is critical to maintaining fluid energy. Fracturing pumps typically pump a very heavy and viscous fluid as the fluid is composed of heavy sand suspended in a gel type fluid. With this type of fluid it is very easy to lose fluid energy to friction and/or turbulence.
A traditional design Suction Manifold is illustrated in FIGS. 2A and 2B. The fluid end sectional view of FIG. 2B is defined in FIG. 2A. An alternate sectional view at a right angle to the sectional view of FIG. 2B is illustrated in FIG. 3B; this sectional view is defined in FIG. 3A. Sharp corners at the intersection of the horizontal main chamber and the vertical suction valve feed ducts result in turbulence and loss of fluid energy. The manifold of this design is a bi-directional flow design.
Zoomie style suction manifolds illustrated in FIGS. 4 and 5, have gained some acceptance in the industry. By intuition, it is incorrectly assumed that that the long sweep ell style ducts reduce turbulence and that the flow in the manifold is uni-directional. However because each suction valve opens and closes at different intervals, flow is actually interrupted when the valve is closed. Furthermore flow is reversed momentarily as the valve closes. When flow reverses, turbulence is generated at the sharp corner positioned at the intersection of the main suction manifold chamber and the ell that functions as a duct for feeding the corresponding suction valve. When the flow stops in a portion of the manifold, some fluid energy is lost and fluid energy is expended to resume flow when the suction valve opens. In addition there is considerable frictional loss in the long sweep ell ducts that the pumped fluid must travel through resulting in even greater loss of fluid energy within the Zoomie style suction manifold.